The present disclosure relates to snowmobiles, and more particularly, the present disclosure relates generally to the frame assembly, suspension assembly, cooling system and air intake system for snowmobiles.
One of the performance characteristics of all vehicles, including snowmobiles, includes the noise, vibration and harshness, the so-called NVH of the vehicle. This includes the comfort of the ride, and depends on a variety of systems and components, including the snowmobile suspension. Typically, a snowmobile suspension includes two systems, a front suspension system for a pair of skis and a rear suspension system for the track.
The front suspension of the snowmobile is coupled to the chassis of the snowmobile and to steerable skis. The front suspension may include one or more suspension arms on each side of the snowmobile.
The rear suspension of a snowmobile supports an endless track driven by the snowmobile engine to propel the machine. The track is supported beneath a vehicle chassis by a suspension that is designed to provide a comfortable ride and to help absorb the shock of the snowmobile crossing uneven terrain. Most modern snowmobiles use a slide rail suspension which incorporates a pair of slide rails along with several idler wheels to support the track in its configuration. The slide rails are typically suspended beneath the chassis by a pair of suspension arms, with each arm being attached at its upper end to the chassis of the snowmobile, and at its lower end to the slide rails.
Noise of the vehicle is also a factor. Intake noise has been a concern for snowmobile designs, and includes the intake noise, that is, the noise from the engine caused by the rush of air flow into the combustion chambers of the engine. Some attempts to control the intake noise are done through air intake silencers. Recent designs have become larger and more complicated and it has become difficult to further reduce intake noise due to a lack of volume available in the engine compartment.
Continued development of snowmobile platforms and the high performance 2-stroke engines that power them have driven platform architecture towards smaller, lighter and more compact integrated systems. As manufacturers push for lighter and smaller vehicles, the engine area space in the snowmobile engine compartment becomes increasingly limited, requiring efficient utilization of non-traditional packaging limitations. One of the areas requiring re-design is the highly tuned and critical 2-stroke exhaust pipe.
In one aspect, a snowmobile comprises a chassis, comprising a front chassis portion and a rear chassis portion; an engine positioned in the front chassis portion and having at least one intake port and at least one exhaust port; a front body portion defined over the front chassis portion and defining an engine compartment; a plenum assembly coupled to the front chassis portion and having at least one intake air vent and at least one air exit opening; and at least one duct coupled to the air exit opening and communicating air to the air intake, the duct being at least partially comprised of a porous material, whereby sound from the air intake is dissipated in the engine compartment.
In yet another embodiment, an exhaust pipe, comprises a diffuser, an expansion chamber, a rear cone, and a stinger tube extending into the rear cone, wherein the stinger tube and rear cone are curved, with centerlines of the stinger tube and rear cone being concentric.
An illustrative embodiment will now be described by way of reference to the drawing figures.